This invention relates to a method for forming heated glass sheets.
Glass sheet forming systems conventionally include a furnace having a heating chamber in which a conveyor conveys glass sheets for heating to a sufficiently hot temperature to permit forming. Normally furnace heating chambers are heated to about 650 to 720xc2x0 C. to provide glass sheet heating to about 620 to 660xc2x0 C. for forming by one or more molds and optional subsequent quenching. U.S. Pat. No. 4,282,026 McMaster et al., U.S. Pat. No. 4,361,432 McMaster et al., U.S. Pat. No. 4,364,765 McMaster et al., and U.S. Pat. No. 4,437,871 McMaster et al. disclose vacuum platens that have a downwardly facing planar surface with spaced holes to which a vacuum is supplied for use in transferring heated glass sheets from a conveyor to a mold on which the glass sheet is formed within the heating chamber of the associated furnace.
While glass sheet forming has previously been conducted externally of a furnace heating chamber as disclosed by U.S. Pat. No. 5,755,845 Woodward et al., the transfer of the glass sheet to such external molds has previously been performed by roller conveyors which require a split mold for passing through the conveyor rolls to perform the forming. While use of external molds is desirable in allowing the use of materials that do not have to withstand the relatively high temperature of a furnace heating chamber, there has not heretofore been an effective system or method for performing glass sheet forming at an external location outside of the furnace heating chamber.
An object of the present invention is to provide an improved system for forming glass sheets.
In carrying out the above objects the system for forming glass sheets in accordance with the invention includes a furnace having a heating chamber including a conveyor for conveying glass sheets for heating sufficiently hot to permit forming of the glass sheets. A vertically movable vacuum platen is located within the heating chamber of the furnace and has a downwardly facing surface to which vacuum is supplied to support a heated glass sheet received from the conveyor. A forming station of the system has a vertically movable upper mold including a downwardly facing forming face, and the forming station and upper mold thereof are located externally of the furnace heating chamber so the upper mold does not have a temperature greater than 500xc2x0 C. A horizontally movable lower ring of the system has an upwardly facing forming face. A first actuator of the system moves the vacuum platen downwardly to a lower position to receive a heated glass sheet from the conveyor and then moves the vacuum platen upwardly to a raised position. A second actuator moves the lower ring horizontally to a first position within tie heating chamber of the furnace below the vacuum platen in the raised position whereupon the lower ring receives a heated glass sheet from the vacuum platen, and the second actuator then moves the lower ring with the heated glass sheet thereon outwardly from the furnace heating chamber to a second position at the forming station below the upper mold. A third actuator of the system moves the upper mold downwardly toward the lower ring in the second position to cooperate with the lower ring in forming the heated glass sheet.
An object of the invention is to provide an improved method for forming glass sheets.
In carrying out the above object, the method for forming glass sheets in accordance with the invention is performed by conveying a glass sheet within a heating chamber of a furnace for heating sufficiently hot to permit forming of the glass sheet. A vacuum platen within the heating chamber of the furnace is moved downwardly to a lower position to receive and support the heated glass sheet and the vacuum platen is then moved upwardly to a raised position with the glass sheet supported by the vacuum platen. A lower ring is then moved into the heating chamber of the furnace to below the vacuum platen in its raised position with the heated glass sheet supported thereby above the lower ring. The heated glass sheet is then released from the vacuum platen and is received by the lower ring. The lower ring is then moved with the heated glass sheet thereon horizontally out of the heating chamber of the furnace to a forming station that includes an upper mold located externally of the furnace heating chamber so the upper mold has a temperature that is not greater than 500xc2x0 C. The upper mold of the forming station is then moved downwardly to cooperate with the lower ring in forming the heated glass sheet.
In carrying out the glass sheet forming method, heat loss of the hot glass sheet is reduced during the forming.
The forming method is also performed utilizing an impulse vacuum that is supplied to the upper mold to assist in the glass sheet forming.
The glass sheet forming method is also disclosed as including moving the formed glass sheet horizontally from the forming station to a cooling station for cooling which may be annealing, heat strengthening or tempering.
The objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.